1. Field of the Invention
The present invention pertains to cannulas having lumens for receiving surgical instruments and, more particularly, to cannulas for being inserted in the body through portals of minimal size allowing various surgical instruments to be introduced in the body via the lumens of the cannulas.
2. Description of the Prior Art
Various least invasive medical procedures involve introducing instruments at operative sites in the body through portals of minimal size formed, such as by puncture or stab wounds, in anatomic walls of the body allowing diverse procedures to be conducted at the operative sites with the operative sites being viewed endoscopically. Such walls include the external skin and underlying soft tissue as well as tissue forming walls of cavities in the body as well as other anatomical structure required to be penetrated to access operative sites in the body. Least invasive medical procedures are particularly useful in joints or articulations of the body, i.e., the connections of the various surfaces of the bones of the body and, especially, the knee, allowing various surgical procedures, such as cartilage repair and ligament repair and reconstruction, to be performed through minimal size portals with the knee being visualized with an arthroscope. Least invasive, closed or endoscopic, surgical procedures possess many advantages over open surgical procedures wherein relatively long incisions are utilized to access an operative site in the body including minimal invasiveness and trauma, reduced hospitalization and rehabilitation times, performance of surgery on an out-patient basis, decreased patient discomfort, enhanced post-surgical mobility and cosmetically pleasing wounds. Accordingly, it is preferred to perform many surgical procedures least invasively, or endoscopically, utilizing very small or narrow portals to access operative sites in the body. In many least invasive surgical procedures, such as arthroscopic posterior cruciate ligament repair and reconstruction of the knee wherein posterolateral or posteromedial portals are formed through the external skin and underlying soft tissue adjacent the knee, the thickness of the tissue forming the walls of the body that must be penetrated to access the operative sites can be considerable such that it is not feasible to introduce and remove instruments directly through portals formed in the tissue of the walls. Accordingly, cannulas are usually inserted through the portals allowing various sizes and types of instruments to be introduced at and removed from the operative sites via lumens of the cannulas with the lumens of the cannulas providing a smooth passage enhancing insertion and removal of the instruments. When inserting cannulas through portals formed in walls of the body, it is desirable that ends of the cannulas disposed within the body remain as close as possible to internal surfaces of the walls such that the ends of the cannulas do not protrude very far into the body to avoid inadvertent contact with and damage to anatomical structure, such as organs, nerves, muscles and other delicate anatomic structure within the body. However, a problem exists with cannulas for receiving medical instruments in that, once the cannulas are inserted through anatomic walls, the cannulas can easily back out of the walls thusly comprising the surgical procedure. Accordingly, there is a need in least invasive, or endoscope, surgical procedures and, in particular, in arthroscopic posterior cruciate ligament procedures of the knee, for cannulas that avoid backing out of anatomic walls through which they are inserted while permitting ends of the cannulas disposed within the body to remain very close to internal surfaces of the walls. Another problem associated with introducing surgical instruments at operative sites in the body through portals formed in tissue of walls of the body is that extravasation can occur; and, therefore, the need exists to prevent extravasation when introducing surgical instruments through portals formed in anatomical walls.
Tubular conduits, such as catheters and needles, for being introduced into the body and having structure, such as rings and collars, for anchoring the conduits in the body have been proposed, and U.S. Pat. No. 4,642,101 to Krolikowski et al, U.S. Pat. No. 3,896,803 to Ekbladh et al, U.S. Pat. No. 3,783,454 to Sausse et al and U.S. Pat. No.2,899,960 to Ginsburg are illustrative of such devices. A disadvantage of such devices is that the conduits are limited to fluid transmission with the body and do not allow instruments to be introduced in the body through the conduits.